The present invention relates to a process for producing an organotitanium compound useful for production of pharmaceuticals and agricultural chemicals and their intermediates and also to a process for addition reaction involving the organotitanium compound. More particularly, the present invention relates to a process for producing an organotitanium compound useful for production of polysubstituted benzene or polysubstituted pyridine.
There is an established process known as Reppe reaction for producing a benzene compound directly from three acetylene compounds in the presence of a catalyst of transition metal catalyst. This reaction, however, has difficulty in producing a polysubstituted benzene compound regioselectively from substituted acetylene compounds.
As for regioselective production of a substituted benzene compound from three acetylene compounds, several processes are disclosed in Chem. Rev. 2000, 100, 2901–2915. These processes are based on condensation of one molecule of diyne compound and one molecule of acetylene compound. Nothing is mentioned about the process of producing a substituted benzene compound regioselectively from three molecules of acetylene compound.
There is known a process for producing a pyridine compound regioselectively from two acetylene compounds and one nitrile compound. (J. Chem. Soc., Dalton 1978, 1278–1282, J. Am. Chem. Soc. 2000, 122, 4994–4995)
The process disclosed in the former literature has the disadvantage of requiring an expensive cobalt complex and being incapable of using two acetylene compounds of different kind. The process disclosed in the latter literature has the disadvantage of requiring an expensive zirconium catalyst and also requiring two-stage reactions with different catalysts. Therefore, both processes are not suitable for industrial production.